Ohm meter
ohmmeter has it's own power supply
an ohmmeter contains its own power source that it uses to test the circuit. if power is still on in the circuit, at the least the meter will give incorrect readings, at the worst the meter may be damaged rendering it useless.
To calibrate an RF power meter, you would typically use a calibrated power source at different known power levels. Connect the power source to the input of the power meter and adjust the calibration settings on the power meter until the displayed power matches the known power levels. Repeat this process at multiple power levels to ensure accuracy across the full range of the power meter.
voltage meter
Most subwoofers have their own power source. There are subwoofers called "passive" woofers that will be powered by your amplifier.
To accurately measure and monitor the energy consumption of your devices using a computer power meter, you can connect the power meter between the device and the power source. The power meter will display real-time data on energy usage, allowing you to track and analyze the power consumption of your devices over time.
Not all switch have there own power source, some of the switches are connected with two or more power sources so it is best to have additional switches to avoid a blowout.
The Audio Technica wireless headset microphone does need its own power source, but the power cord is very small and discreet.
Each research station provides its own power source from its own power plant. Field camps use portable means for power, and primarily these are gas powered.
Research stations generate their own power, usually from gas-generated motors.
Usually RFID tags would get the power from the reader.
The Bird power meter for rf power.